JP2002032001A - Holographic storage medium, method of manufacturing the same, and holographic storage device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for lessening the influence of a temperature fluctuation on stored holographic information. SOLUTION: The holographic memory medium and the method for manufacturing the same as well as the holographic memory device including the memory medium are provided. In one embodiment, the holographic memory medium includes (a) first and second substrates (205 and 210) of which the first substrate is plastic and which are arranged apart a spacing and (2) a photopolymer core (215) arranged between the first and second substrates. This photopolymer core has such a coefficient of thermal expansion that the first and second substrates and the photopolymer core substantially isotropically respond with the temperature change.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to storage devices, and more particularly, to a holographic storage system and method having an enhanced temperature operating range.

[0002]

2. Description of the Related Art Technologies that support the development of enhanced information systems are an area of primary focus. Optical storage of data has been one of the lights of these technologies in the past few years.
For example, compact discs dominate the market for music recordings and are now the standard medium for multimedia releases where text, images and sounds can be combined. A compact disc can hold about 640 megabytes,
This is 300, double-spaced sentences
High fidelity of 000 pages or 1 hour and 15 minutes
y) Can accommodate music. However, the development of information storage devices has been sought in order to increase the storage capacity.

As part of this development, page-wise memory systems using holographic storage have been proposed as alternatives to conventional memory devices. A page-wise memory system for storing one page of data involves storing and retrieving a complete two-dimensional representation. Typically, a record or "writing"
Light passes through a two-dimensional array of dark and transparent areas that represent data. The holographic system then stores the data in three dimensions, and the holographic representation of the page results as a pattern of varying refractive index imprinted on the storage medium.

[0004] Holographic data storage typically involves the angular bandwidth of recorded data pages.
The distribution of the grating that changes the tilt angle at intervals proportional to the period generated by ndwidth
n). The reconstructed or “readout” light is defined by the well-defined angle of incidence (Bragg angle (Br
agg angle)). For background information on holographic systems, see Scientific, by D. Psaltis et al.
HolographicMemorie by American, November (1995)
s.

[0005] Photopolymer materials are considered as attractive recording media candidates for high density holographic data storage. These are low cost, easily processed and have high photosensitivities.
ty) can be designed to have a large index contrast. This class of materials provides the dynamic range, media thickness, optical quality and dimensional stability required for high density applications.
y). This is the "R" by Lisa Dhar et al.
ecording Media That Exhibit High Dynamic Range for
Holographic Storage ", Optics Letters, Volume 24,
P.487 (1999). One area of drawback of these materials is their rather large coefficient of thermal expansion, which causes dimensional changes in the material with changes in temperature.

[0006] Polymer materials for holographic recording are typically sandwiched between two substrates to ensure high light quality. At present, glass substrates are
Used to sandwich polymeric materials. The dimensional changes caused by temperature fluctuations of the polymer in the glass substrate indicate anisotropy such that the fluctuations occur primarily in the direction of the thickness (perpendicular to the plane of the substrate). This occurs because the polymer material is constrained by the substrate in a transverse (parallel to the plane of the substrate) direction and is only allowed to move in the thickness direction.

This anisotropic temperature response is approximately three times greater than the effect of the anisotropic temperature response.
Has a negative effect on This behavior severely limits the acceptable operating temperature range for the use of the material as a holographic data storage medium. For background information on the anisotropic temperature effect, see "Temperature-Induced by Lisa Dhar et al.
Changes in Photopolymer Volume Holograms ", Applie
d Physics Letter, Volume 73 No. 10, 1337 (1998).

[0008]

What is needed in the art is a method for reducing the effects of temperature fluctuations on stored holographic information.

[0009]

SUMMARY OF THE INVENTION In order to overcome the above-mentioned disadvantages of the prior art, the present invention provides a holographic storage medium, a method of manufacturing a holographic storage medium, and a holographic storage device including the storage medium. .
In one embodiment, the holographic storage medium is
(1) substrates arranged at first and second intervals,
The first substrate is plastic, and (2) disposed between the first and second substrates, such that the first and second substrates and the photopolymer core respond substantially substantially to temperature changes. A photopolymer core having a coefficient of thermal expansion such that it cooperates with.

According to the invention, the dimensional stability of at least one substrate of the holographic storage medium is not always desirable, the mechanical compatibility between the core and the at least one substrate, the thermal expansion, etc. The importance of becoming anisotropic and having smaller optical effects has been recognized.

For the purposes of the present invention, the term “substantially isotropically responsive” refers to the operation with respect to Bragg Angle Shifts of the materials used to construct the holographic storage medium. It means that the limit is that the thermal expansion is not exceeded. Those skilled in the art are familiar with Bragg angle shift. Alternatively, the response may not be substantially isotropic, but the degree of anisotropy is such that the enhanced operating temperature range is maintained without causing unacceptable write or read errors Things. The effects described above have been described for holograms multiplexed in a volume using a single hologram as well as any currently or future developed multiplexing techniques. For example, angle multiplex
ing), wavelength multiplexing, phase correlation multiplexing, aperture multiplexing, shift multiplexing, and phase code multiplexing.

[0012] The photopolymer core also includes an anisotropic material as well as a photoactive monomer system. A photoactive monomer system is a system that includes a monomer that polymerizes upon incidence of light. Photoactive monomer systems are used in photopolymers that use polymerization as a recording mechanism and are well known to those skilled in the art.

In one embodiment of the present invention, the coefficient of thermal expansion of the photopolymer core is about 5 times that of the first substrate.
It ranges from 0% to about 500%. In a related embodiment, the coefficient of thermal expansion of the photopolymer core ranges from about 50% to about 500% of the coefficient of thermal expansion of the second substrate.

[0014] In one embodiment of the invention, the second substrate is plastic. In one embodiment illustrated and described, the second substrate is made of, but need not be, the same material as the first substrate and has the same lateral dimensions. In other embodiments of the present invention, the materials forming the first and second substrates may be different or the same.

In one embodiment of the present invention, the optical effect of the coefficient of thermal expansion of the polymer core is wavelength dependent. In another embodiment of the present invention, the optical effect of the coefficient of thermal expansion of the photopolymer core can be compensated for by adjusting the wavelength of the readout laser. This allows a tunable laser to be used to further compensate for optical variations caused by thermal expansion or contraction.

In one embodiment of the present invention, a portion of the photopolymer core is a photoactive monomer system. In another embodiment of the present invention, the entire photopolymer core is a photoactive monomer system.

In one embodiment of the invention, the exposure polymerizes the photopolymer core or a portion of the photopolymer core. However, chemical or structural changes in the core that signify the presence, degree or absence of interaction are within the broad scope of the invention.

In one embodiment of the present invention, the present invention provides:
Provide a holographic storage device that includes: (1) Coherent light source. (2) A holographic multiplexing mechanism that causes a change in the interaction between the object beam and the reference beam obtained from the coherent light source. (3) a holographic storage medium for receiving and storing an interference pattern resulting from the interaction, wherein (A) a first and second spaced substrate being plastic;
And (B) a photopolymer core disposed between the first and second substrates, wherein the first and second substrates and the photopolymer core are substantially isotropically responsive to temperature changes. With a coefficient of thermal expansion that cooperates with each other.

For the purposes of the present invention, the term "causing an interaction change" means that the holographic multiplexing mechanism can cause a change in the period or phase of the grating in the interaction. . Of course, however, other types of changes to the interaction are also within the broad scope of the present invention.

[0020]

DETAILED DESCRIPTION OF THE INVENTION In FIG. 1, angle multiplexing (angle) configured to create and capture holographic images constructed in accordance with the principles of the present invention.
A block diagram of one embodiment of a holographic storage system 100 that uses multiplexing is shown. The illustrated embodiment uses angle multiplexing, while other embodiments use other holographic multiplexes, such as wavelength multiplexing, phase correlation multiplexing, aperture multiplexing, shift multiplexing, and phase code multiplexing. Any scheme or mechanism that can be used, and techniques developed in the future, are also within the broad scope of the invention.

The system 100 is an ordinary computer 1
And a holographic storage device 110 having an enhanced temperature operating range. The holographic storage device 110 is used for the object display 11.
5, including a coherent light source 120, a conventional light steering mechanism 125, a holographic storage medium 130 and a control unit 135. FIG. 1 shows a holographic storage device 110 configured to store or write a holographic image of an object appearing on an object display 115 to a holographic storage medium 130.

In the illustrated embodiment, object display 115 is coupled to computer 105 and receives digital information to be stored on holographic storage medium 130. The multi-bit digital data stream is arranged into an array or data page and provided to the system using the object display 115. In one embodiment, the object display 115 is a holographic storage medium 1
A liquid crystal display (LCD) screen that represents 1's or 0's by a transparent or opaque square pattern to be stored or written in 30.

In another embodiment, object display 115 can be any spatial-light modulator. Those skilled in the art are familiar with the use of spatial-light modulators. A modulated beam from a spatial light modulator is imaged, Fourier transformed, or relayed to holographic storage medium 130 using optical elements well known to those skilled in the art.

The coherent light source 120 is a tunable laser directed to the light steering mechanism 125. Light steering mechanism 125, a holographic multiplexing mechanism for angle multiplexing, changes the angle of incidence of the beam on holographic storage medium. Each hologram multiplexed at the same location in the holographic storage medium 130 is stored at a different angle. The holographic storage medium 130 receives and stores an interference pattern resulting from the interaction between the object beam from the object display 115 and the reference beam from the light steering mechanism 125.

The control unit 135 includes the computer 10
5 is also coupled to the holographic storage device 1 by adjusting all aspects of the writing light, the object to be scanned, the management of the generated holographic image and the positioning of the storage medium.
10 operations are managed. Those skilled in the art are familiar with the use of tunable lasers. For background information on holographic systems, see Holographi, D. Psaltis et al.
c Memories, Scientific American, November (1995).

In one embodiment, holographic storage medium 130 includes first and second spaced plastic substrates and a photopolymer core (see FIG. 3 for further details of the holographic storage medium). ). The photopolymer core is located between the first and second substrates and has a coefficient of thermal expansion that approximately matches the coefficients of thermal expansion of the first and second substrates. Proper matching of the coefficients of thermal expansion can be achieved with the holographic storage medium 130.
Allows for a substantially isotropic response to changes in operating temperature.

The substantially isotropic change of the holographic storage medium 130 allows the stored holographic image to be restored with acceptable fidelity over an extended operating temperature range. This range is extended by the fact that isotropic changes are smaller than anisotropic changes. Also, isotropic changes, expansions or contractions can be compensated for by changes in the readout wavelength.

Referring to FIG. 2, one embodiment of a holographic storage system 101 configured to recreate and restore holographic data pages stored on a holographic storage medium 130 configured in accordance with the principles of the present invention. FIG. System 101 includes a computer 105 and a holographic storage device 110 having an enhanced temperature operating range. The holographic storage device 110 includes the coherent light source 1
20, including a light steering mechanism 125, a holographic storage medium 130, a sensor 140 and a control unit 135.

The holographic storage device 110
A holographic image of a data page stored in the holographic storage medium 130 is configured to be read. The coherent light source 120 is a tunable laser that provides readout light to a holographic storage medium 130 through a light steering mechanism 125. The reading light is applied to the holographic storage medium 1
Interfering with or diffracting the dielectric modulation stored in 30 to recover the digital data page.

The different data pages are addressed by using the light steering mechanism 125 to change the angle of the reference beam. The reconstructed digital data page is imaged on sensor 140 with all bits in the data page detected at the same time. One skilled in the art is familiar with the use of sensor arrays or detector units, such as sensors 140, in holographic storage systems.

Sensor 140 sends the recreated holographic data page to computer 105 for further processing. Typically, error correction codes and channel modulation codes are used to recover digital data. The control unit 135 includes the computer 1
05 to adjust the wavelength of the coherent light source 120 and a light steering mechanism 125.
Coordinate all aspects of reading stored holographic data pages for the holographic storage device 110, such as controlling the holographic storage device 110. Background information on restoring holographic images in holographic systems can be found in Hologr by D. Psaltis et al.
aphic Memories, Scientific American, November (199
It is shown in 5).

Referring to FIG. 3, a diagram of one embodiment of a holographic storage medium 200 used in the holographic storage device 110 of FIGS. 1 and 2 is shown. The holographic storage medium 200 includes first and second substrates 205, 210 spaced apart and a photopolymer core 215 located between the substrates.
Photopolymer core 215 includes a light interference pattern 220 that is written during holographic recording.

In the embodiment shown, photopolymer core 215 is polymerized by exposing photopolymer core 215 to light. The first and second substrates 205 and 210 and the photopolymer core 215 are
Cooperate to respond substantially isotropically to temperature changes.

In another embodiment, photopolymer core 215 has a coefficient of thermal expansion ranging from about 50% to about 500% of the coefficient of thermal expansion of first substrate 205. In a related embodiment, the coefficient of thermal expansion of the photopolymer core 215 ranges from about 50% to about 500% of the coefficient of thermal expansion of the second substrate 210.

In the illustrated embodiment, a portion of the photopolymer core 215 is a photosensitive monomer system. In an alternative embodiment, the holographic storage medium 20
The presence, degree, or absence of interactions within the zero core may be represented by other chemical or structural changes that may be used to represent or represent the light interference pattern 220.

FIG. 3 shows some typical characteristics of the light interference pattern 220 whose readout characteristics depend on temperature. The light interference pattern 220 is characterized by a grating period Λ, as shown in FIG. 3, and by a tilt angle Φ indicating a deviation from the vertical indicated by the light interference pattern 220. Also, the Bragg angle shift ΔΘ
_B indicates a shift in the direction required by the incident read light from the original recording position to obtain Bragg matching. For further reference, see Tempera by Lisa Dhar et al.
ture-induced changes in photopolymer volume hologr
ams ", AppliedPhysics letters, Volume 73, No. 10, p
See 1337 (1998). Those skilled in the art are familiar with grating periods, tilt angles, Bragg matching and Bragg angle shifts.

The anisotropic temperature response greatly limits the temperature range over which these parameters change and maintain acceptable fidelity of the recreated object. Alternatively, the substantially isotropic temperature response shown in the illustrated embodiment of the invention reduces the required Bragg shift. Thus, this property maintains acceptable fidelity of the regenerated object for the enhanced temperature range.

Also, while the temperature response of the holographic storage medium 200 may not be substantially isotropic, the degree of anisotropy is such that the enhanced operating temperature range may cause unacceptable write or read errors. It can be such that it is maintained without receiving. In the illustrated embodiment, the optical effect of the coefficient of thermal expansion of the photopolymer core 215 can be neutralized by changing the wavelength of the laser. This allows the tunable laser to be advantageously used as the coherent light source 120 of FIGS. 1 and 2 to further compensate for optical variations caused by thermal expansion or contraction. However, a change in the wavelength of the laser causes a change in the optical magnification that appears in recording or writing. This change in magnification can be modified appropriately to restore the original magnification of the data page to be detected.

Generally, the first and second substrates 205, 2
10 may include the same or different materials. In the illustrated embodiment, the second substrate 210 comprises the same material, plastic, as the first substrate 205. Also, the second
The substrate 210 of this does not need to be so,
It has the same lateral dimension as the first substrate 205.

FIG. 4 shows a graph 300 illustrating the theoretical temperature response for different types of holographic storage media. Graph 300 includes first, second, and third curves 305, 310, 315. The first curve 305 shows the temperature response for a holographic storage medium using a photosensitive core located between two glass substrates. This structure shows an unacceptable anisotropic response to temperature fluctuations. This first curve 305 shows that for a temperature increase of 15 degrees Celsius, the Bragg angle shift is 0.
Indicates that it is outside the twice indicated acceptable operating range. This degree of Bragg angle shift distorts fidelity to unacceptable levels when using readout light to regenerate objects from storage.

The second curve 310 shows the temperature response for the holographic storage medium 200 of FIG. Here, the photopolymer core 215 and the first and second substrates 205, 210 produce a substantially isotropic temperature response. In the illustrated embodiment, holographic storage medium 200 has a substantially isotropic response that produces a Bragg angle shift of about 0.1 degrees for the same temperature increase of 15 degrees Celsius. This Bragg angle shift is about one-half of the entire allowable operating range. However, this shift
It appears to occur in the lower half of the acceptable range, which effectively reduces the acceptable range.

The third curve 315 shows the temperature response for the holographic storage medium of FIG. 3 when wavelength tuning is used. Adjusting the read light wavelength effectively relocates the second curve 310 to the center of an acceptable operating range, as shown. The ability to relocate or adjust this temperature response would actually extend the temperature range of acceptable fidelity for recreating objects from storage.

One skilled in the art should understand that the present invention is not limited to a Bragg angle shift of about 0.1 degrees or any other absolute value. The present invention also does not require the use of wavelength tuning. Other embodiments may use the same or different types of photosensitive cores and produce different Bragg angle shifts resulting in a wider operating temperature range and greater write and read reliability.

In FIG. 5, a graph 350 showing the experimental temperature response for two holographic storage media is shown. Graph 350 includes first and second curves 360,370. The first curve 360 represents a 250 accommodated between two glass substrates 1 millimeter thick.
Figure 4 shows the temperature response for a holographic storage medium using a micrometer thick photopolymer layer. The second curve 370 represents a 500 micrometer thick 2
Figure 4 shows the temperature response for a holographic storage medium using a 250 micrometer thick photopolymer layer contained between two polycarbonate substrates.

[0045] Bragg detunin
g) The level shift was measured at a temperature about 6.7 degrees Celsius above the temperature in recording the hologram. It can be observed that the shift range for the photopolymer contained on the plastic substrate (second curve 370) is about a power of two less than the shift range of the photopolymer material contained on the glass substrate (first curve 360). For details of the experiment, see "Temperature-induced chang" by Lisa Dhar et al.
es in photopolymer volume holograms ", Applied Phys
ics letters, Volume 73, No. 10, p 1337 (1998), which uses an experimental setup similar to that used to obtain the data of FIG.

Referring to FIG. 6, a flowchart of one embodiment of a method 400 for manufacturing a holographic storage medium constructed in accordance with the principles of the present invention is shown. Method 40
0 starts at step 405 with the selection of acceptable plastics for use as the first and second substrates. Step 405 also includes selecting the appropriate photopolymer to use as the core.

In one embodiment, step 405 includes:
Selecting a photopolymer core having a coefficient of thermal expansion such that the first and second substrates and the photopolymer core cooperate to respond substantially isotropically to temperature changes. In a second embodiment, the photopolymer core comprises:
The first substrate has a coefficient of thermal expansion ranging from about 50% to about 500% of the coefficient of thermal expansion. In a third embodiment, the photopolymer core further has a coefficient of thermal expansion ranging from about 50% to about 500% of the coefficient of thermal expansion of the second substrate.

In step 410, the first and second
Is formed to have a suitable thickness and shape for the intended holographic storage medium and holographic storage device. Then, the photopolymer core is added at step 415 to 2
Formed between two substrates. The method 400 includes step 42
Exit at 0, where the holographic storage medium is properly tested and packaged.

Those skilled in the art should understand that the present invention is not limited to the manufacturing process described above. Other embodiments of the invention can use other manufacturing processes and can have additional or fewer steps than those described above.

In summary, the present invention states that dimensional stability in at least one substrate of the holographic storage medium is not always desirable, but rather that the thermal expansion is substantially isotropic and thus the optical effects are less. Mechanical compatibility between the core and the at least one substrate is more important in that it is less. This results in a wider operating temperature range for the media and greater write and read reliability. The operating temperature range can typically be further extended by at least the use of readout wavelength tuning.

[0051]

As described above, according to the present invention, it is possible to provide a method for reducing the influence of temperature fluctuation on stored holographic information.

The number in parentheses after the requirements of the invention in the claims indicates the relationship of the embodiments of the present invention, and should be interpreted as limiting the scope of the present invention. Not be.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating one embodiment of a holographic storage system that uses angular multiplexing configured to generate and capture holographic images constructed in accordance with the principles of the present invention.

FIG. 2 is a block diagram illustrating one embodiment of a holographic storage system configured to regenerate and restore holographic data pages stored on a holographic storage medium configured in accordance with the principles of the present invention.

FIG. 3 illustrates one embodiment of a holographic storage medium used in the holographic storage device of FIG.

FIG. 4 shows theoretical temperature responses for different types of holographic storage media.

FIG. 5 shows an experimental temperature response for two holographic storage media.

FIG. 6 is a flowchart illustrating one embodiment of a method of manufacturing a holographic storage medium constructed in accordance with the principles of the present invention.

[Explanation of symbols]

 Reference Signs List 100,101 holographic storage system 105 computer 110 holographic storage device writing configuration 115 object display 120 coherent light source 125 light steering mechanism 130 holographic storage medium 135 control unit 140 sensor 200 holographic storage medium 205 first substrate 210 second Substrate 215 Photopolymer core 220 Light interference pattern

 ──────────────────────────────────────────────────続 き Continuation of the front page (71) Applicant 596077259 600 Mountain Avenue, Murray Hill, New Jersey 07974-0636 U.S.A. S. A. (72) Inventor Kevin Richard Curtis United States, 07974 New Jersey, New Providence, Hickson Drive 193 (72) Inventor Lisa Dar United States, 07974 New Jersey, New Providence, Springfield Avenue 1200, Upper Mention 1C (72) Inventor Melinda Lamont Snooz Henry Street 312 F-term (reference) 2K008 AA04 AA11 DD01 DD12 FF07 HH01 HH26 5B003 AA09 AC01 AC01

Claims (22)

[Claims] 1. A first and a second spaced apart arrangement.
And a photopolymer core disposed between the first and second substrates, wherein the first substrate is plastic, and wherein the photopolymer core includes the first and second substrates and A holographic storage medium, characterized in that the photopolymer core has a coefficient of thermal expansion that cooperates to respond substantially isotropically to temperature changes. 2. The thermal expansion coefficient of the photopolymer core is:
2. The holographic storage medium according to claim 1, wherein the holographic storage medium is in a range of 50% to 500% of a thermal expansion coefficient of the first substrate. 3. The thermal expansion coefficient of the photopolymer core is:
3. The holographic storage medium according to claim 2, wherein the holographic storage medium is in a range of 50% to 500% of a coefficient of thermal expansion of the second substrate. 4. The holographic storage medium according to claim 1, wherein said second substrate is made of plastic. 5. The holographic storage medium according to claim 1, wherein the optical effect of the coefficient of thermal expansion of the photopolymer core is wavelength-dependent. 6. The holographic storage medium according to claim 1, wherein a part of the photopolymer core is based on a photosensitive monomer. 7. The holographic storage medium of claim 1, wherein the exposing polymerizes the photopolymer core. 8. The method of claim 1, further comprising: forming a first plastic substrate; forming a second substrate; forming a photopolymer core between the first and second substrates; A method of manufacturing a holographic storage medium, wherein the core has a coefficient of thermal expansion such that the first substrate and the photopolymer core cooperate to respond substantially isotropically to temperature changes. . 9. The thermal expansion coefficient of the photopolymer core is:
9. The method of claim 8, wherein the thermal expansion coefficient is in a range of 50% to 500% of the first substrate. 10. The thermal expansion coefficient of the photopolymer core is 50% to 500% of the thermal expansion coefficient of the second substrate.
10. The method of claim 9, wherein the value is in the range of%. 11. The second substrate is plastic, and the photopolymer core cooperates so that the second substrate and the photopolymer core cooperate in a substantially isotropic manner to temperature changes. 9. The method of claim 8, wherein the method has an expansion coefficient. 12. The method of claim 8, wherein the coefficient of thermal expansion of the photopolymer core is wavelength dependent. 13. The method of claim 8, wherein a portion of the photopolymer core is a photosensitive monomer system. 14. The method of claim 8, wherein exposing causes the photopolymer core to polymerize. 15. A coherent light source; a holographic multiplexing mechanism for effecting a change in an interaction between an object beam and a reference beam obtained from the coherent light source; and receiving an interference pattern resulting from the interaction; A holographic storage medium for storing, wherein the holographic storage medium is spaced between first and second substrates, both of which are plastic, and disposed between the first and second substrates. Wherein the photopolymer core has a thermal expansion such that the first and second substrates and the photopolymer core cooperate in a substantially isotropic response to a temperature change. A holographic storage device having coefficients. 16. The thermal expansion coefficient of the photopolymer core is in the range of 50% to 500% of the thermal expansion coefficients of the first and second substrates.
A holographic storage device as described. 17. The holographic storage device according to claim 15, wherein the coherent light source generates read light that interacts with the interference pattern to recreate the interaction. 18. The holographic storage device according to claim 17, wherein the holographic multiplexing steering mechanism causes the readout light to interact with the interference pattern. 19. The holographic storage device of claim 15, wherein the optical effect of the coefficient of thermal expansion of the photopolymer core is compensated by adjusting the wavelength of the laser source. 20. The holographic storage device of claim 19, wherein said optical effects are further compensated by changing optical magnification in response to adjusting the wavelength. 21. The holographic storage device according to claim 15, wherein a portion of the photopolymer core is based on a photosensitive monomer. 22. The holographic multiplexing mechanism is one selected from the group consisting of angle multiplexing, wavelength multiplexing, phase correlation multiplexing, aperture multiplexing, shift multiplexing, and phase code multiplexing. 2. The method according to claim 1, wherein
The holographic storage device of claim 5.